Sawdust reinvented into sponge for oil spills

The material is environmentally friendly and modified to soak up to five times its weight in oil and float for months in icy, rough waters

US Researchers have chemically modified sawdust to make it oil-attracting and buoyant, characteristics that make it ideal for cleaning oil spills the cold waters of the Arctic.

The nontoxic material comes from sawmill waste that is discarded onto home garage floors to soak up oil spilled by amateur mechanics and absorbs up to five times its weight in oil and stays afloat for at least four months, according to the researchers.

George Bonheyo, a microbiologist at the Department of Energy’s Pacific Northwest National Laboratory (PNNL), said: "Most of today's oil remediation materials are designed for warm water use. But as ice retreats in the Arctic Sea, fossil fuel developers are looking north, and we need new oil spill response methods that perform well in extreme conditions.”

Containing oil spills in cold waters is especially problematic, as bobbing ice chunks push oil below the water's surface, making it difficult to collect. The same goes for rough waters, where tall, clashing waves disperse oil.

The modified sawdust can also control oil burns. If changing weather or tides move spilled oil toward a sensitive area quickly, oil can be burned before it can cause further harm. Called in-situ burning, the practice can significantly reduce the amount of oil in water and minimise its adverse environmental effects.

To enable the dust to soak up oil, researchers chemically attached components of vegetable oil onto the material's surface. These attachments make the modified material oil-attracting and hydrophobic. The final product is a light, fluffy, bleached powder. The team is also contemplating adding small, oil-eating microbes - fungi and bacteria - to the powder's surface so any left-behind material could naturally break down oil over time.

The modified sawdust is applied by sprinkling a thin layer over oil on the water's surface. The material immediately starts soaking up oil, creating a concentrated and solid slick that stays afloat thanks to the material's buoyant nature. The oil-soaked material can either be burned or retrieved.

Tests have shown the material's water-repellent nature prevents ice from forming on it. Early results from oil burn tests indicate that a small amount of material enables burning of both thin and thick layers of spilled oil.

In the coming months, PNNL will further evaluate the modified sawdust. The material will need additional testing and approval by multiple agencies before it can be used at actual oil spills.